Allow update of protected branches

[hoerup]

In gitlab 15.6 gitlab finally added api support to update protected branch settings, so ProjectProtectedBranch should be updated accordingly

https://gitlab.com/gitlab-org/gitlab/-/issues/20229/

[nejch]

This is a premium feature and we'll need to add a http_patch method for this as well.

Edit: And once the Free version PUT endpoint is implemented, we kind of need to be able to distinguish that in the .save() and .update() methods.

[JohnVillalovos]

Link to the API docs:

https://docs.gitlab.com/ee/api/protected_branches.html#update-a-protected-branch

[Hokwang]

I think free version will have this endpoint. We know gitlab developers, right?
How about provide .save() or .update() anyway?